PROJECT SUMMARY The goal of this equipment request is to acquire a new ultracentrifuge instrument and a pair of new Ti45 ultracentrifuge rotors. These items will enable purification of large quantities of tubulin protein with far greater efficiency than has been possible using the borrowed and aging equipment on which we currently rely. Purified tubulin is a fundamental resource required for all of our biophysical studies of the mitotic spindle machinery. Purified tubulin is also required for our collaborations with several local NIH?funded laboratories.